Curable adhesive compounds and bonding or filling compounds are widely used for structurally connecting object surfaces together or for filling gaps, openings and cavities in an object surface. Such curable compounds are generally manipulated and positioned on the object surface in a semi-solid state and are then hardened or cured in position to a more solid and permanent state. The curing or hardening of applicable compounds is generally a chemical process which is promoted and driven by one or more curing conditions or factors. For example, the curing process may be driven by exposure of the semi-solid compound and components thereof to air or by exposure of such a compound and its components to an energy source, such as a heat source.
Other curable adhesive and filling compounds are cured by exposure to radiated energy, such as visible and non-visible light energy. Such compounds, referred to as light-curable compounds, are manipulated in a semi-solid form into an area or onto a work surface. Light radiation, preferably in the form of a light beam at a specific wavelength or band of wavelengths, is then directed onto the compound. The compound includes light-sensitive chemical components therein which, when exposed to the light at the specific wavelength, promote the curing or hardening of the compound in the desired position on the work surface to bond, fill, or coat the surface.
As an example, light-curable filling and adhesive compounds are widely used in dental procedures. Dentists use light-curable dental compounds for coating and sealing tooth surfaces, filling caries and other cavities in the tooth surface, and securing crowns and various other dental structures to a tooth surface. Conventionally, dental compounds are cured by exposure to light in the blue range of the spectrum. Once cured, the dental compound reduces further tooth decay, bonds the dental structure, and/or provides additional structure to a tooth. Therefore, it is important that the compounds are completely cured.
More specifically, for curing light-curable dental compounds, visible blue light, and particularly a blue light beam from a hand-held curing light device, is directed onto a tooth surface containing the desired compound layer. The blue light penetrates into the compound layer on the tooth surface for complete curing. The duration of the exposure to blue light for proper curing of the compound layer is dictated by the type of compound and the thickness of the compound layer, as well as the power level and characteristics of the blue light from the curing light device. For example, a thin tooth surface coating or veneer will require less radiated light power, while thicker, deeper fillings for caries and other cavities will require a greater amount of radiated power directed onto the tooth surface for proper curing.
While light-curable compounds have shown very beneficial results in the dental field, existing techniques and dental curing light devices utilized to deliver the light to the tooth surface have various drawbacks. For example, existing dental curing devices require specific filtering mechanisms. Filtering must be done for several reasons. First, it is known that certain wavelengths of blue light are harmful to human tissue. While attempts are made to direct the light beam only on to the tooth surface, a certain amount of oral tissue exposure to the light is inevitable. Therefore, harmful wavelengths must be filtered. Additionally, light-curable compounds are usually sensitive to light having a somewhat specific wavelength, such as a specific blue light wavelength with currently available dental compounds. Therefore, a dental curing light filtering device is tuned to emit light at the proper wavelengths for both patient safety and proper curing.
Many existing conventional dental curing lights use broad spectrum lamp elements, such as halogen bulbs. As a result, dental curing lights must utilize special and complicated filtering devices or filters which receive the broad spectrum light from the lamp element, and then filter the light to provide only the light at the desirable wavelengths. Available lamp elements deliver a wide spectrum of radiation, including visible light, UV light, and infra-red light. Therefore, prior art curing techniques and light devices have generally been very inefficient, because a large amount of the radiated light power is lost simply due to filtering of a significant part of the light spectrum. For example, the input power to a conventional halogen bulb may typically be around 80 Watts, whereas the output power from the dental light device of light at the desired blue wavelength, for example 400–500 nanometers, is typically less than one-half (0.5) Watt.
Additionally, the efficiency of the prior art dental curing lights is further degraded by power losses due to the angle of incidence of the radiated light upon the filtering element. For example, many prior art curing lights utilize reflective filters which reflect only the light at the desirable wavelengths, such as blue light, onto the tooth surface and dental compound. Light at the undesirable wavelengths is passed through the filter to a light absorbing component where it is dissipated. If the angle of incidence of the light from the halogen bulb varies significantly from the desired angle of incidence for the filtering element surface (e.g., 45°), then a reduced amount of the desirable light is reflected onto the tooth surface. This further decreases the amount of desirable light power which is available for curing the dental compound. Conversely, a higher amount of light at undesirable wavelengths may also be reflected onto the tooth surface, rather than being transmitted through the filtering element to be dissipated.
Still another drawback with prior art curing lights is that they generate significant amounts of heat and therefore require complicated cooling systems to operate within the proper temperature range. The significant amount of light energy at the undesirable wavelengths, which is generated by the halogen bulb, must be filtered or otherwise captured. The captured or filtered energy is then dissipated in the form of heat. Therefore, power absorbing and heat dissipating elements are required within conventional curing light devices.
Thermal shields are often utilized in conjunction with reflective filters to absorb and dissipate the unreflected, unused light energy in the form of heat. The high power output required for the halogen bulb to produce the desired light power level for curing, creates a significantly high thermal load on the shields. The shields must then be cooled. Generally, fan elements are used in the dental light device to provide convective cooling to the shields. The additional cooling elements increase the size of the light device and complicate its design. As will be appreciated, it is desirable to keep the light device as small and maneuverable as possible, since it is hand-held and used in a patient's mouth.
Additionally, a thermal load is also placed on the reflective filter element, which must then also be cooled, such as by heat sinks and fans. The absorption devices and heat dissipating systems not only complicate the operation and design of the light device, but also make it more expensive to produce, and more subject to operational failure.
Another drawback of prior art dental curing light devices is the limited operational life of the lamp element, such as a halogen bulb. The bulbs frequently burn out and must be replaced. Furthermore, the heat generated inside the light device, which is usually enclosed, shortens the effective operational lifespan of the bulb.
Attempts have been made in the prior art to address some of these drawbacks. For example, Japanese Patent Applications No. 6-30275, 6-285508, 7-163863, and 8-194786; U.S. Pat. Nos. 5,420,768 and 5,634,711; and U.K. patent application No. GB 2,329,756, all disclose various devices using packaged, conventional light-emitting diodes or LEDs, to provide a curing light source with light in the desirable blue range. While specific blue light is provided by the LEDs without significant filtering, various of these devices require complicated internal designs for focusing of the curing light, or require specific electronic control of the LEDs. Furthermore, large numbers of conventional LEDs are necessary. As illustrated in the Figures of those applications, the solid state LED elements are spread out over a circuit board or other support structure and require a somewhat large housing to contain all of the conventional LEDs necessary for generating the intensity of light which is required for practical curing uses. Therefore, it has been difficult to provide a suitable curing light using conventional LEDs, which will generate sufficient curing power in a small incomplete design.
Using traditional packaged LEDs, as disclosed in the above-cited art, has specifically presented difficulties associated with generating sufficient curing power within a reasonably sized device which may be adequately cooled. Further complications with such devices have resulted from attempts to concentrate the light from the large grouping of traditional LEDs into a small area and at a sufficient power density so as to be useful for curing. Such difficulties in providing a suitable curing light device utilizing the existing traditional packaged LED technology is highlighted by the lack of a well-received and widely-utilized dental curing light on the market which utilizes such technology.
Alternatively, the devices and technology disclosed in U.S. patent application Ser. No. 09/009,205, noted above, have provided a curing device with solid state, light-emitting components which generate sufficient curing power densities in a reasonably-sized device that may be properly cooled. Further efforts by the inventors of the present application are continuing to improve the existing technology disclosed in that earlier application and to provide the desirable curing power density, size and thermal characteristics required for a successful commercial curing device.
Still another drawback associated with prior art curing lights is their inefficiency in transmitting the light to the work surface, such as a tooth surface, once the light has been generated by the element or bulb. The light is generated within the main housing of the curing light, and must be transmitted to an output end of the housing. Existing dental curing lights utilize elongated light guides to deliver light from the light generating elements inside the housing to the tooth.
Light guides are usually comprised of a large number of optical fibers fused together into an elongated guide. The air/glass interfaces between the generating elements and the input end of the light guide and the output end of the light guide and the inside of the mouth are inefficient and may produce approximately a 10% loss in power per interface. Furthermore, prior art devices may utilize a converging lens to focus light into the input end of the light guide. This provides another lossy interface encountered by the light. Such inefficiencies further increase the cure time that is necessary, and/or create the need for higher power (and associated heat) to provide the necessary curing light intensity.
Another concern with dental curing lights is that such lights are medical/dental instruments, and a portion of the instrument is introduced into a cavity of the body, i.e. the mouth. Since the same curing light will be utilized with different patients, cross-contamination between patents must be avoided. Accordingly, sterilization of the curing light, or a portion thereof, has been necessary with conventional devices. Sterilization, often referred to as autoclaving, requires additional equipment which must be purchased and maintained by the dentist or other physician. Sterilization also introduces an extra step in between curing procedures. Furthermore, the high heat required for sterilization may, over time, damage components of the curing light. Accordingly, conventional curing lights must be designed to withstand sterilization and the high temperatures associated therewith of to otherwise address the sterilization issue.
Accordingly, it is an objective of the present invention to provide a simple, durable curing light device for hardening or curing light-curable compounds. Particularly, it is an objective to provide such a curing light device for curing dental compounds used for dental fillings and coatings.
It is another objective to provide a curing light utilizing solid state light elements.
It is another objective to provide a curing light which has a compact and simple design and which is capable of providing a light power density that is useful for practical curing applications.
It is still another objective of the present invention to cure compounds with curing lights utilizing less power and having greater efficiency to reduce the amount of heat energy generated by the device and thus reduce the heat energy which must be dissipated. Furthermore, it is desirable to provide more efficient cooling of the light-generating devices.
It is still another objective of the invention to eliminate the necessity of reflective filters and other filter elements within a light device for curing light-curable compounds.
It is still another objective to address the need for sterility within a curing light.
It is still a further objective to provide a blue light device which operates within a small space and is easily manipulated within the mouth of a dental patient.
These objectives and various other objectives will become more readily apparent from the Description of the Invention below.